Navigation systems have become known in the art as computer-based systems that are mounted in a vehicle for calculating a driving route to a final destination input by the driver and outputting driving indications for guiding the driver to the desired destination. The driving indications include announcements and instructions relating to forthcoming driving maneuvers, which have to be performed by the driver in order to follow the calculated driving route. The driving maneuvers are determined by the navigation system based upon the calculated driving route (i.e. crossings, junctions and the like) and output to the driver, typically by an audio-response unit for voice output of the navigation system.
More specifically, once a driving route to a final destination has been calculated, the navigation system determines the driving maneuvers that have to be performed by the driver at different points (locations) along the route while following the calculated driving route from the starting point to the final destination.
Subsequently, when the vehicle, which is traveling along the calculated driving route, approaches the point of the route where a driving maneuver should be performed, different driving indications relating to the forthcoming driving maneuver are output sequentially to the driver based upon the distance to the respective point of the route.
As to the content of such driving indications, they typically comprise different announcements of the forthcoming maneuver. For example, at first, a general announcement such as “turn off to the right coming soon” at a rather long distance of 400-700 m may be output, followed by an advance announcement of the imminent maneuver including the distance to the maneuver, such as “turn off to the right after 100 meters”, and, finally, in the immediate vicinity of the point of the maneuver, the instruction to perform the driving maneuver such as “now turn off to the right”.
However, these different announcements output sequentially by the navigation system may be confusing for the driver, in particular if she/he is not familiar with the use of a navigation system. Furthermore, it happens that the indications given by speech output via the audio response unit are missed or misinterpreted by the driver. As a result, it occurs that the driver does not comply with the instructions output by the navigation system, which—in the worst case—may lead to a significant deviation between the position of the vehicle and the calculated route which should be followed by the driver, i.e., to wrong-way-driving.
In such a case, if the vehicle leaves the calculated driving route and wrong-way-driving, i.e., a predetermined significant positional deviation between the set position of the vehicle according to the predetermined driving route and the actual position of the vehicle, is determined by the navigation system by comparison of the actual position of the vehicle and the calculated driving route, a modified driving route is calculated by the navigation system. As an example, EP 0 833 291 B1 describes details relating to a method for “re-searching” the driving route when the vehicle is out of the calculated route. Such a method may include a search for an entirely new route to the final destination from the current position of the vehicle, or, alternatively, the calculation of an additional route for returning to the original driving route calculated previously.
In both cases, the driver is provided with additional driving indications as to the additional maneuvers that have to be performed according to the newly calculated modified driving route. Nevertheless, in any case a modified driving route means a detour as compared to the original route, which of course, should be avoided.